Mitomycin C is an antitumor antibiotic which can be obtained by culturing a strain of Streptomyces caespitosus and is widely used clinically.
Various methods for purifying mitomycin C from the culture medium harvested after the culture of the above-mentioned bacterial strain are conventionally known. For example, included are an activated carbon adsorption method which comprises adding activated carbon to the culture supernatant separated from the bacterial cells by filtration to allow mitomycin C to adsorb thereto, followed by eluting mitomycin C with an organic solvent; and a method which comprises transferring mitomycin C in the culture supernatant to an organic phase, concentrating the organic phase, purifying the mitomycin C-containing concentrate by alumina chromatography or counter current distribution, concentrating the mitomycin C-containing eluate to dryness, and adding a small amount of acetone to the resulting solid to give crystals (Patent Literature 1).
Another known method comprises allowing mitomycin C in the culture medium to adsorb to a reverse-phase adsorption resin; eluting mitomycin C with a solvent such as acetone, methanol and ethanol; concentrating the eluate to remove the solvent, followed by sodium chloride saturation and phase transfer to chloroform; subjecting the chloroform extract to alumina column chromatography for separation and elution of mitomycin C; concentrating the eluate into a dense solution of mitomycin C in methanol, followed by adding ether, petroleum ether, benzine or ligroine to this solution to give pure mitomycin C crystals; concentrating the mother liquor as well, followed by repeating the same procedure as above to give crude crystals; and washing the crude crystals with a mixture of 10% methanol and ether to give pure mitomycin C crystals (Patent Literature 2).
Yet another known method comprises allowing mitomycin C in the culture medium to adsorb to a reverse-phase adsorption resin; eluting mitomycin C with ethyl acetate; evaporating off the solvent in the eluate; allowing mitomycin C in the residue to adsorb to a reverse-phase adsorbent with a small particle size; eluting mitomycin C with hydrous methanol; allowing mitomycin C in the eluate to adsorb to a reverse-phase adsorption resin; eluting mitomycin C from the resin with methanol; and concentrating the eluate to crystallize mitomycin C (Patent literature 3).
Also known is a method which uses a solvent system consisting of a combination of a mitomycin C-soluble solvent and a poor solvent for the production of mitomycin C crystals (Patent Literature 4).